Pee shivers: You know you're curious

When grown men and little boys urinate, occasionally our entire body is abruptly racked with a mysterious, internal blast of cold that makes us visibly shudder from the shoulders down. It typically occurs near the end of the task, lasting roughly one frigid second.

This chill is not discussed, of course, in polite circles -- or even when we return to our buds in the sports bar. So, at no time will you hear: “Dudes, you’ll never guess what just happened to me in the bathroom?” Well … hopefully never.

Yet, we’ve given this sensation a name: the pee shiver. And as the name suggests, depending on a guy’s aim, it can make for messy results.

So let’s get right to question No. 1.

Why, in the name of Wiz Khalifa (or, if you like, P. Diddy), does this happen?

“No one knows for certain what the specific trigger for the shivering is,” says Sheth, formerly director of the gastrointestinal motility program at Yale Medical School. But he points to two generally accepted variables to help solve this riddle.

First, the feeling “mostly” is experienced by males. Second, it “occurs most commonly while voiding large amounts of urine,” he says.

Or, to put it as delicately as possible, the icy jolt seems to hit after we’ve really, really had to go. Never after a tiny trickle.

According to Sheth, our parasympathetic nervous system (responsible for “rest-and-digest” functions) lowers the body’s blood pressure “to initiate urination.” One leading theory behind the shudder is that peeing can unleash a reactive response from the body’s sympathetic nervous system (which handles “fight or flight” actions).

On the cellular level, the body is theoretically flushed with catecholamines (which you know better as chemicals like dopamine or hormones like adrenaline). Those are dispatched to help restore or maintain blood pressure, Sheth says. But the microscopic energy bullets “may also trigger the shiver reflect.”

This theory, the author says, best explains “the gender difference as men pee standing up and, therefore, would be more prone to feeling the effects of a lower blood pressure, thereby triggering this exaggerated sympathetic nervous system response.

“Anecdotally,” he adds, “I don’t believe I have ever experienced the post-pee shivers while sitting down.” This would suggest that women don't tend to get them. (Do you? If so, please let us know.)

“I wouldn't know if it's a guy thing or a girl thing because I've never had a conversation with a girl about this – and it's not likely to happen anytime soon,” says stand-up comedian Dan Nainan

“I always wonder: what is that? … Why is it happening?” Nainan adds. “Obviously there is an evolutionary or natural-selection reason for everything. (But) as I'm trying to picture a caveman urinating out in the open, I'm wondering what the necessity of the shivering is.

“I think it tends to happen more in a public bathroom,” he adds. “Could it be some sort of way to warn off nearby enemies or something?”

Wow, comics must have to endure some pretty rough bathrooms.

Bill Briggs is a frequent contributor to msnbc.com and author of “The Third Miracle.”